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View Full Version : How to take out background from video/ making a matte



cupidslate
05-10-2007, 02:17 AM
hey guys,

My questions is, i have filmed a person in a room doing movement, and i want to know how to take out the background, and use lightwave to make smoke coming up from the ground and going around the person, then enveloping the person and, after that the smoke moves back down to the ground and the person is no longer there,..... i have filmed the background also without the person, so for compositing,.... but how do i get the smoke to animate around the person, thats the tricky bit,.... please can any1 help??:help:

G M D THREE
05-10-2007, 07:29 AM
I assume you didn't shoot the person on green screen. Therefore you have to roto him, so you can composite the smoke around him.

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norlight
05-10-2007, 08:04 AM
Assuming you didnīt move the camera you could be lucky and be able to pull out rhe background by using a difference operator in a compositor.

As for the smoke, one way of dealing with it in LW is to make a stand-in box wherever the person in the scene is located.

Then you can do your smokeanimation and have your stand-in box be unseen by camera at rendertime.

Finally this needs to be composited ina compositor like Combustion/AE etc.

cupidslate
05-11-2007, 03:43 PM
thanks guys.... anything else u would suggest,... for example what if (if) i had moved the camera around the person,.... i would have to then do the match moving process,... but can i still do the other stuff u suggested??

Digital Hermit
05-11-2007, 08:45 PM
If you can, give us a frame grab so we can see the condition of the shot, then some of us can illustrate what can be done.

In addition, we could give better advice knowing what type of video software you own...

(DH whispers to himself, "Please don't say movie maker... please don't say movie maker!" )

Regards,

cupidslate
05-11-2007, 11:00 PM
video editing software i use is edius pro3,...... dont have specific footage in format at the moment.... but i am wondering does any1 know how to rotoscope properly step by step??

G M D THREE
05-12-2007, 06:09 PM
video editing software i use is edius pro3,...... dont have specific footage in format at the moment.... but i am wondering does any1 know how to rotoscope properly step by step??

You started your question with: i have filmed a person in a room doing movement. Now you say you don't have specific footage!?

No offense but if you have to ask how to roto my guess is that you are aiming to high with doing a composite with a particle animation. Its like asking how to do a car stunt jumping true a burning hoop and than ask for a basic drivers lesson. ...lol

This is how its done in a basic way. Shoot person on green or blue screen. Shoot a clean backplate. Once the footage keyed out, export the footage and its alpha as a image seq. Make a 4 point poly object in the proportions of your footage. Apply the the color footage as texture in the color channel and the alpha into the trancparency channel. Set luminosity to 100%, Defuse to 0%, Specular 0%, Reflection 0%. Load it into layout, do your smoke animation around your person who is basicly a moving card board figure. Smart way is to render person and smoke separately so you can tweak his diapering in the composite over your back plate.

Keep camera locked, on your shoot, as a moving camera opens a big can of worms like 3d camera tracking or use of motion control rig.

My explanation is just small synopsis of what is usually covered in entire books, as there is way more to it, alone on the compositing end of it.

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Surrealist.
05-15-2007, 10:20 PM
You can take a look here on this thread (http://www.spinquad.com/forums/showthread.php?t=17578) for some info as well.